eBay / PayPal will withold funds for new sellers until a track record has been established - This information is from the eBay help pages:

While you establish your selling track record, buyer payments may be delayed. These funds will generally be available once:

It's been more than 90 days since your first successful sale; and
You've had more than 25 sales transactions; and
You've had more than $250 in total sales.

If you meet that criteria and are still having your payments held, I'd contact PayPal to request the holds be lifted. Some further information in this thread might help if you aren't able to get them to lift the hold: http://community.ebay.com.au/t5/Selling/21-DAY-HOLD-FINANCIAL-SERVICE-OMBUDSMAN-WANTS-TO-HEAR-FROM-Y...